Hantavirus cardiopulmonary syndrome resulting from any of a number of hantaviruses in the western hemisphere is thought to be contracted through inhalation of infected rodent excreta. In southern and central Chile, the Andes virus infects the sigmodontine rodent Oligoryzomys longicaudatus, and causes a rare but severe human infection with high mortality. In western Panama, the Choclo virus infects the rodent Oligoryzomys fulvescens and causes a common but usually mild or inapparent human infection with a low mortality rate. In both regions the risk of transmission appears to be influenced by many factors increasing the opportunity for close contact between infected rodents and susceptible humans. We will focus our investigations on three of these factors, with the goal of gaining insights critical for the design of future environmental interventions to decrease hantavirus transmission. First, recent investigations in Chile and Panama have associated risk of infection with selected vegetation habitats favored by the infected vector rodents. In Chile exposure risk can be predicted by remote sensing with satellite imagery analysis over 2/3 of the country. In Panama a micro scale analysis has suggested complex relationships between peridomestic infected rodents and agricultural activities. We propose to focus on spatial relationships between rodents and habitats over time, using mark-recapture trapping and radiotelemetry to mark rodent movements, particularly in peridomestic environments. Second we will create a dynamic model that extends our current static analysis of risk. The new model will apply graph theory to field collected data of rodent habitat preferences and movements within the landscape to predict the likely movement of infected rodents. We will test the model using data from sites different from those used to create the model. The temporal precision of the model will be improved by quantitating viral load in rodent blood, tissue and urine in the winter (low transmission) and spring (high transmission) seasons. Finally, serial serosurveys of at-risk human populations in Panama will quantify the impact on human infection associated with spatial-temporal variations in rodent density and movement.